Alveolar Arterial Gradient and Respiratory Index in Pre-dicting the Outcome of COVID-19 Patients; a Retrospec-tive Cross-Sectional Study

Alveolar arterial (A-a) oxygen gradient and respiratory index can be of immense help for the crit-ical care physician in clinical decision making. This study aimed to evaluate the potential application of A-aoxygen gradient and respiratory index in predicting the survival of COVID-19 patients in intensive care unit(ICU).

This is a retrospective cross-sectional study involving 215 adult patients with COVID-19 dis-ease, admitted to the ICU between 1st April 2020 and 30 June 2021. Details regarding demographic variables,comorbidities, laboratory and arterial blood gas (ABG) findings were recorded. Alveolar-arterial gradient andrespiratory index were calculated and tested as predictors of survival.

The mean age of the patients was51.92 years (65.6 % male). Hypertension was the most common comorbidity and oxygen via non-rebreathingmask was the most common modality used at the time of ICU admission. Mortality was 28.37% and averagelength of stay was 12.84 days. Patients who died were older (p=0.02), mostly male (p=0.017), had at least onecomorbidity (p<0.001), and higher heart rate and respiratory rate (<0.001 and p=0.03, respectively), lower pHon arterial blood gas (ABG) (p=0.002), higher FiO2 requirement (p<0.001), and increased A-a oxygen gradienton admission compared to survivors. According to receiver operating characteristic (ROC) curve analysis, A-aoxygen gradient and respiratory index were not sensitive or specific in predicting mortality in the studied pa-tient subset.

A-a oxygen gradient and respiratory index calculated at time of admission to ICU inpatients with COVID-19 were poor predictors of survival